Frogs That Hear With Their Mouth
September 4, 2013 – A small frog that lives in the Republic of Seychelles has its senses a bit jumbled up– it listens with its mouth instead of its ears!
New research has found that the frogs, known as Gardiner's frogs, don't have a middle ear or eardrum like we do. Most four-legged animals have middle ears which are made of tiny bones that take vibrations from the eardrum and turn them into sound waves on their way to the cochlea.
If humans and four-legged animals didn't have a middle ear and an eardrum we would all be deaf, but, strangely enough, these frogs aren't.
Scientists have long been confused about why a frog would have such a distinct squeaky croak if none of the other frogs of its species could hear it.
To see if Gardiner's frogs actually do use sound to communicate with each other the study's scientists set up speakers in the rain forests of Seychelles and played frog songs. Male Gardiner's frogs responded to the songs with their croaks, which meant they could hear the recording.
To find out how they could hear researchers used X-ray imaging to look inside the frogs' heads and found that they use only their mouth cavities to pick up the croaks of other frogs. The mouth makes the sound frequencies louder and the sounds travel through tissue and bones (which are thinner than those in other frog species) in the skull to the inner ear.
Lead study researcher Renaud Boistel of the French National Center for Scientific Research explained "The combination of a mouth cavity and bone conduction allows Gardiner's frogs to [hear] sound effectively without use of a middle ear."